Surface acoustic wave filter with temperature sensor

ABSTRACT

Aspects of this disclosure relate to a surface acoustic wave filter with an integrated temperature sensor. The integrated temperature sensor can be a resistive thermal device configured as a reflective grating for a surface acoustic wave resonator, for example. A radio frequency system can provide over temperature protection by reducing a power level of a radio frequency signal provided to the surface acoustic wave filter responsive to an indication of temperature provided by the integrated temperature sensor satisfying a threshold.

CROSS REFERENCE TO PRIORITY APPLICATIONS

Any and all applications for which a foreign or domestic priority claimis identified in the Application Data Sheet as filed with the presentapplication are hereby incorporated by reference under 37 CFR § 1.57.This application claims the benefit of priority under 35 U.S.C. § 119(e)of U.S. Provisional Patent Application No. 62/437,519, filed Dec. 21,2016 and titled “SURFACE ACOUSTIC WAVE FILTER WITH TEMPERATURE SENSOR,”the disclosure of which is hereby incorporated by reference in itsentirety herein. This application claims the benefit of priority under35 U.S.C. § 119(e) of U.S. Provisional Patent Application No.62/437,544, filed Dec. 21, 2016 and titled “FILTER WITH OVER TEMPERATUREPROTECTION,” the disclosure of which is hereby incorporated by referencein its entirety herein.

BACKGROUND Technical Field

Embodiments of this disclosure relate to a filter with a temperaturesensor and/or providing over temperature protection for a filter.

Description of Related Technology

A filter, such as an acoustic wave filter, can filter a radio frequency(RF) signal. Example acoustic wave filters include surface acoustic wave(SAW) filters and bulk acoustic wave (BAW) filters. A film bulk acousticresonator (FBAR) filter is an example of a BAW filter.

Acoustic wave filters can be implemented in radio frequency electronicsystems. For instance, filters in a radio frequency front end of amobile phone can include acoustic wave filters. Receiving an inputsignal having a sufficiently high power can damage an acoustic wavefilter.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of this disclosure will now be described, by way ofnon-limiting example, with reference to the accompanying drawings.

FIG. 1A is a schematic diagram of a radio frequency system with overtemperature protection according to an embodiment.

FIG. 1B is a schematic diagram of an example over temperature circuitaccording to an embodiment.

FIG. 2A is a schematic diagram of a radio frequency system with overtemperature protection according to another embodiment.

FIG. 2B is a schematic diagram of a radio frequency system with overtemperature protection according to another embodiment.

FIG. 3 is a schematic diagram of a radio frequency system with overtemperature protection according to another embodiment.

FIG. 4 is a schematic diagram of a radio frequency system with overtemperature protection according to another embodiment.

FIG. 5A is a schematic diagram of an acoustic wave filter with aresistive thermal device according to an embodiment.

FIG. 5B is a schematic diagram of an acoustic wave filter with aresistive thermal device and off die circuit elements coupled to theresistive thermal device according to an embodiment.

FIG. 5C is a schematic diagram of an acoustic wave filter with aresistive thermal device and off die circuit elements coupled to theresistive thermal device according to another embodiment.

FIG. 6 is a schematic diagram of an acoustic wave filter with aresistive thermal device according to another embodiment.

FIG. 7 is a schematic diagram of an acoustic wave filter with aresistive thermal device according to another embodiment.

FIG. 8 is a schematic diagram of an acoustic wave filter with aresistive thermal device according to another embodiment.

FIG. 9 is schematic diagram of an acoustic wave filter with resistivethermal devices according to an embodiment.

FIG. 10 is schematic diagram of an acoustic wave filter with anintegrated temperature sensor that includes a thermocouple according toan embodiment.

FIG. 11 is schematic diagram of an acoustic wave filter with anintegrated temperature sensor that includes a resonator according to anembodiment.

FIG. 12A is schematic block diagram of a duplexer that includes atransmit filter with an integrated temperature sensor according to anembodiment.

FIG. 12B is schematic block diagram of a duplexer that includes atransmit filter with a first integrated temperature sensor and a receivefilter with a second integrated temperature sensor according to anembodiment.

FIG. 12C is schematic block diagram of a duplexer that includes areceive filter with an integrated temperature sensor according to anembodiment.

FIG. 13 is graph of a transfer function of a duplexer over frequency inwhich a shift in the transfer function can result in an out of bandblocker failure.

FIG. 14 is graph that zooms in on transmit and receive pass bands of thegraph of FIG. 13.

FIG. 15 is a simulated heat map of a surface acoustic wave duplexer.

FIG. 16A is a block diagram of a layout of an acoustic wave filter withan integrated resistive thermal device according to an embodiment.

FIG. 16B is a block diagram of a layout of an acoustic wave filter withan integrated resistive thermal device according to another embodiment.

FIG. 17A illustrates a serpentine resistive thermal device configured asa grating for a surface acoustic wave resonator according to anembodiment.

FIG. 17B illustrates a serpentine resistive thermal device configured asa grating for a surface acoustic wave resonator according to anotherembodiment.

FIG. 18 illustrates a portion of a surface acoustic wave filter with anintegrated resistive thermal device according to an embodiment.

FIG. 19 illustrates a larger portion of the surface acoustic wave filterof FIG. 18.

FIG. 20 is a schematic block diagram of a module that includes a filterand an over temperature circuit according to an embodiment.

FIG. 21 is a schematic block diagram of a module that includes a filterand an over temperature circuit according to another embodiment.

FIG. 22 is a schematic block diagram of a module that includes a filterand an over temperature circuit according to another embodiment.

FIG. 23 is a schematic block diagram of a module that includes a filterand an over temperature circuit according to another embodiment.

FIG. 24 is a wireless communication device that includes a radiofrequency front end that can include a filter with an integratedtemperature sensor according to one or more embodiments.

SUMMARY OF CERTAIN INVENTIVE ASPECTS

The innovations described in the claims each have several aspects, nosingle one of which is solely responsible for its desirable attributes.Without limiting the scope of the claims, some prominent features ofthis disclosure will now be briefly described.

One aspect of this disclosure is a surface acoustic wave filter thatincludes surface acoustic wave resonators and a resistive thermaldevice. The surface acoustic wave resonators are configured to filter aradio frequency signal. The resistive thermal device has a resistancethat changes with temperature. The resistive thermal device includesmetal strips arranged in series with each other. The resistive thermaldevice is configured as a reflective grating of a surface acoustic waveresonator of the surface acoustic wave resonators.

The resistive thermal device can be connected between an input port ofthe surface acoustic wave filter and ground. The resistive thermaldevice can be connected to a dedicated temperature sensing port of thesurface acoustic wave filter. The resistive thermal device can beconnected between an output port of the surface acoustic wave filter andground. The resistive thermal device can be positioned adjacent to anarea of the surface acoustic wave filter having a high power dissipationrelative to other areas of the surface acoustic wave filter.

The resistive thermal device can have a resistance of at least 500Ω. Theresistive thermal device can have a resistance of at least 1 kΩ. Theresistive thermal device can have a resistance in a range from 1 kΩ to10 kΩ.

The metal strips can form a serpentine shape in plan view. The metalstrips can include aluminum.

The resistive thermal device can be further configured as a reflectivegrating for a second surface acoustic wave resonator of the surfaceacoustic wave resonators.

The surface acoustic wave filter can be a transmit filter.

Another aspect of this disclosure is a radio frequency system with overtemperature protection. The radio frequency system includes a surfaceacoustic wave filter, a radio frequency signal path, and an overtemperature circuit. The surface acoustic wave filter is configured tofilter a radio frequency signal. The surface acoustic wave filterincludes an integrated temperature sensor. The radio frequency signalpath is configured to provide the radio frequency signal to the surfaceacoustic wave filter. The over temperature circuit is configured toreduce a power level of the radio frequency signal responsive to anindication of temperature provided by the temperature sensor satisfyinga threshold.

The integrated temperature sensor can include a resistive thermal devicehaving a resistance that changes with temperature. The resistive thermaldevice can be arranged as a grating for at least one surface acousticwave resonator of the surface acoustic wave filter. Alternatively, thetemperature sensor can include a thermocouple, a resonator, or athermistor.

The over temperature circuit can reduce the power level of the radiofrequency signal to a safe level responsive to the indication oftemperature provided by the temperature sensor satisfying the threshold.The safe level can represent a power level that is below a specifiedupper bound on a power level of an input to a surface acoustic wavefilter. A radio frequency signal at the safe level should not damage thesurface acoustic wave filter.

The radio frequency signal path can be a transmit signal path. The radiofrequency signal path can include a power amplifier operatively coupledto the surface acoustic wave filter. The over temperature circuit canreduce a power level of an input of the power amplifier. Alternativelyor additionally, the over temperature circuit can attenuate an output ofthe power amplifier. In some instances, the over temperature circuit candecouple the radio frequency signal from an input to the surfaceacoustic wave filter using a switch.

The radio frequency system can include one or more suitable features ofthe surface acoustic wave filters discussed herein.

Another aspect of this disclosure is a packaged module that includes asurface acoustic wave filter, an over temperature circuit, and a packageenclosing the surface acoustic wave filter and the over temperaturecircuit. The surface acoustic wave filter is configured to filter aradio frequency signal. The surface acoustic wave filter includes anintegrated temperature sensor. The over temperature circuit isoperatively coupled to the integrated temperature sensor. The overtemperature circuit is configured to reduce a power level of the radiofrequency signal responsive to an indication of temperature provided bythe temperature sensor satisfying a threshold.

The packaged module can include a second surface acoustic wave filterthat includes a second integrated temperature sensor.

The surface acoustic wave filter can be a transmit filter of amultiplexer. The multiplexer can be duplexer. Alternatively, the surfaceacoustic wave filter can be implemented as a stand-alone transmitfilter.

The packaged module can include a second acoustic wave filter and amulti-throw switch enclosed within the package, in which the multi-throwhas a first throw coupled to the surface acoustic wave filter and asecond throw coupled to the second acoustic wave filter. The packagedmodule can also include a second multi-throw switch enclosed within thepackage, in which the surface acoustic wave filter is coupled betweenthe multi-throw switch and the second multi-throw switch.

The packaged module can include one or more suitable features of thesurface acoustic wave filters and/or the radio frequency systemsdiscussed herein.

Another aspect of this disclosure is a radio frequency system with overtemperature protection. The radio frequency system includes a transmitsignal path configured to provide a radio frequency signal, a transmitfilter coupled between the transmit signal path and an antenna port, andan over temperature circuit. The transmit filter is configured to filterthe radio frequency signal. The transmit filter includes an integratedtemperature sensor. The over temperature circuit is configured to reducea power level of the radio frequency signal responsive to an indicationof temperature provided by the integrated temperature sensor satisfyinga threshold.

The transmit filter can be an acoustic wave filter. The integratedtemperature sensor can include a resistive thermal device arranged as agrating of a surface acoustic wave resonator of the acoustic wavefilter. The resistive thermal device can also be arranged as a gratingof a second surface acoustic wave resonator of the acoustic wave filter.The acoustic wave filter can be a surface acoustic wave filter. Theacoustic wave filter can be a bulk acoustic wave filter, such as a filmbulk acoustic resonator filter.

The over temperature circuit can reduce the power level of the radiofrequency signal to a safe level responsive to the indication oftemperature provided by the temperature sensor satisfying the threshold.The safe level can represent a power level that is below a specifiedupper bound on a power level of an input to a surface acoustic wavefilter. A radio frequency signal at the safe level should not damage thesurface acoustic wave filter.

The transmit signal path can include a power amplifier operativelycoupled to the transmit filter. The over temperature circuit can reducea power level of an input of the power amplifier. Alternatively oradditionally, the over temperature circuit can attenuate an output ofthe power amplifier. The over temperature circuit can decouple the radiofrequency signal from an input to the transmit filter using a switch incertain instances.

The integrated temperature sensor can include a resistive thermaldevice. The integrated temperature alternatively can include athermocouple, a resonator, or a thermistor.

The temperature sensor can be connected between an input port of thetransmit filter and ground. Alternatively, the temperature sensor can beconnected between an output port of the transmit filter and ground. Thetemperature sensor can be connected between a dedicated temperaturesensing port of the transmit filter and ground. The temperature sensorcan have a first end coupled to a first port of the transmit filter anda second end coupled to a second port of the transmit filter.

Another aspect of this disclosure is a packaged module that includes atransmit filter configured to filter a radio frequency signal, an overtemperature circuit, and a package enclosing the transmit filter and theover temperature circuit. The transmit filter includes an integratedtemperature sensor. The over temperature circuit is operatively coupledto the integrated temperature sensor. The over temperature circuit isconfigured to reduce a power level of the radio frequency signalresponsive to an indication of temperature provided by the temperaturesensor satisfying a threshold.

The packaged module can include a second transmit filter that includes asecond integrated temperature sensor.

The transmit filter can be included in a multiplexer. The multiplexercan be a duplexer. Alternatively, the transmit filter can be configuredas a stand-alone transmit filter.

The packaged module can include a second transmit filter and amulti-throw switch enclosed within the package, in which the multi-throwhas a first throw coupled to the transmit filter and a second throwcoupled to the second transmit filter. The packaged module can alsoinclude a second multi-throw switch enclosed within the package, thetransmit filter being coupled between the multi-throw switch and thesecond multi-throw switch.

The packaged module can include one or more suitable features of thetransmit filters and/or the radio frequency systems discussed herein.

Another aspect of this disclosure is a wireless communication device.The wireless communication device include a radio frequency front endand an antenna operatively coupled to a transmit filter of the radiofrequency front end. The radio frequency front end includes a transmitfilter configured to filter a radio frequency signal. The transmitfilter includes an integrated temperature sensor. The radio frequencyfront end also includes an over temperature circuit configured to reducea power level of the radio frequency signal responsive to an indicationof temperature provided by the integrated temperature sensor satisfyinga threshold.

The wireless communication device can be a mobile phone.

The wireless communication device can include a transceiver incommunication with the radio frequency front end, in which the overtemperature circuit configured to provide an over temperature signal tothe transceiver to reduce the power level of the radio frequency signal.

The wireless communication device can include one or more suitablefeatures of any of the transmit filters discussed herein, any of theradio frequency systems discussed herein, any of the packaged modulesdiscussed herein, or any combination thereof.

Another aspect of this disclosure is a method of over temperatureprotection in a radio frequency system. The method includes providing anindication of temperature of a filter using a temperature sensorintegrated in the filter, the filter being configured to filter a radiofrequency signal; detecting that the indication of temperature of thefilter satisfies a threshold; and in response to the detecting, reducinga power level of the radio frequency signal provided to the filter.

The filter can be a surface acoustic wave filter and the integratedtemperature sensor can be a resistive thermal device.

Reducing the power level of the radio frequency signal can includereducing a power level of an input signal to a power amplifier that isoperatively coupled to the filter. Reducing the power level of the radiofrequency signal can include decoupling a power amplifier from thefilter.

The method can include transmitting the radio frequency signal using anantenna of a mobile device.

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features of the innovations have been described herein. It isto be understood that not necessarily all such advantages may beachieved in accordance with any particular embodiment. Thus, theinnovations may be embodied or carried out in a manner that achieves oroptimizes one advantage or group of advantages as taught herein withoutnecessarily achieving other advantages as may be taught or suggestedherein.

The present disclosure relates to U.S. patent application Ser. No.15/848,768, titled “FILTER WITH OVER TEMPERATURE PROTECTION,” filed oneven date herewith, the entire disclosure of which is herebyincorporated by reference herein.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

The following detailed description of certain embodiments presentsvarious descriptions of specific embodiments. However, the innovationsdescribed herein can be embodied in a multitude of different ways, forexample, as defined and covered by the claims. In this description,reference is made to the drawings where like reference numerals canindicate identical or functionally similar elements. It will beunderstood that elements illustrated in the figures are not necessarilydrawn to scale. Moreover, it will be understood that certain embodimentscan include more elements than illustrated in a drawing and/or a subsetof the elements illustrated in a drawing. Further, some embodiments canincorporate any suitable combination of features from two or moredrawings.

A filter, such as a surface acoustic wave filter, in a transmit path ofa cellular handset can be damaged if an input power of a signal providedto the filter is too high. The filter can be implemented in amultiplexer, such as a duplexer. A closed-loop power controller canattempt to maintain a substantially constant forward power out of anantenna of the cellular handset by adjusting the input power from atransceiver to compensate for varying loss at the antenna of thecellular handset. In certain high Voltage Standing Wave Ratio (VSWR)scenarios, an output loss can be sufficiently high that, in an attemptto maintain a desired power out of the antenna, the input power of thesignal provided by the filter can be pushed beyond the limits of thefilter. This can irreparably damage the filter in some instances.

To avoid damage to filters due to relatively high input power of asignal provided to a filter input, some filters have been designed towithstand relatively extreme power and VSWR conditions. However, thiscan add significant challenges to the filter design process and canlimit how small the physical size of a filter can be.

Dissipated power in a filter or duplexer can manifest as thermal energy(e.g., a locally elevated temperature on a filter die). Accordingly, agiven amount of dissipated power can generate a correspondingtemperature rise. Failure events, such as damage to the filter, can bepreceded by an excessive rise in temperature. By integrating atemperature sensor onto the filter substrate adjacent to an area ofrelatively high power dissipation, the dissipated power can be monitoredin situ. An over temperature circuit can be implemented to reduce inputpower to the filter in response to a particular temperature thresholdbeing exceeded. The over temperature circuit can be implemented using arelatively straightforward complementary metal oxide semiconductor(CMOS) circuit or other similar technology.

A surface acoustic wave (SAW) filter typically includes a plurality ofSAW resonators, each of which can include at least two reflectivegratings. The gratings can be arranged to reflect acoustic energy.Accordingly, the gratings can be referred to as acoustic reflectors. Oneor more of the gratings can include a plurality of periodicallydistributed relatively thin metal strips connected electrically inparallel with each other. Because these metal strips are part of theacoustically active area of a SAW filter, the electrode geometry can beprecisely controlled. Taking advantage of precisely controlled metalstrip geometry, a highly reproducible resistive thermal device (RTD) canbe formed by reconfiguring the parallel connected metal strips of one ormore reflective gratings into series connections. The resistance of theresistive thermal device changes with temperature. By chaining arelatively large number of reflective strips together in series, aresistive thermal device having relatively large resistance can berealized. The relatively large resistance can be at least a kilo-Ohm(kΩ) or several kilo-Ohms.

If the resistance of the resistive thermal device is sufficiently large(e.g., at least 500Ω or at least 1 kΩ), the resistive thermal device canbe connected in shunt with an existing direct current (DC) blockedfilter input or filter output to allow temperature monitoring withoutextra device connections. Connecting the resistive thermal device inshunt with an existing DC blocked filter input or filter output canallow temperature monitoring without significantly increasing insertionloss. For example, in a typical 50Ω system, a shunt-connected resistanceof 3.5 kΩ can add only about 0.05 dB of additional insertion loss.

Since a resistive thermal device of series connected metal strips canreconfigure existing device geometries of a SAW filter, the resistivethermal device can be implemented without consuming extra area on thefilter die. A SAW filter with an integrated resistive thermal deviceformed of series connected reflective gratings can be included in arelatively inexpensive solution that can relax ruggedness requirementsand allow filter size and cost reductions.

Aspects of this disclosure relate to preventing irreparable damage to afilter due to certain VSWR conditions, which can be a catastrophic eventwithout over temperature projection for the filter. Reducing the filterinput power and/or shutting off a power amplifier in a transmit patharranged to provide a radio frequency signal to the filter are some waysto prevent damage to the filter due to excessive heating. Using anindication of temperature provided by an integrated temperature sensor,such as an RTD, an over temperature circuit can detect conditions thatcould cause irreparable damage to the filter and prevent such damage tothe filter.

A serpentine resistive thermal device or another integrated temperaturesensor can be implemented on bulk acoustic wave (BAW) filters and/orother filter technologies. BAW filters can be manufactured with tightlycontrolled metal processes that can be used to form an RTD. This canresult in RTDs with precise resistances that can be formed in arepeatable manner.

Any principles and advantages discussed herein can be applied to avariety of radio frequency (RF) systems as suitable. Such radiofrequency systems can implement over temperature protection. Anintegrated temperature sensor of a filter can provide an indication oftemperature of the filter to an over temperature circuit. The overtemperature circuit can detect whether an output of the integratedtemperature sensor satisfies a threshold. Responsive to the output ofthe temperature sensor satisfying the threshold (e.g., exceeding thethreshold), the over temperature circuit can reduce a power level and/orsignal level of a radio frequency signal provided to the filter. Theover temperature circuit can reduce the power level and/or signal levelof the radio frequency signal in any suitable manner. FIGS. 1A, 2A, 2B,3, and 4 provide examples of radio frequency systems with overtemperature protection. Any suitable combination of features of theseradio frequency systems can be implemented.

FIG. 1A is a schematic diagram of a radio frequency system 10 with overtemperature protection according to an embodiment. As illustrated, theradio frequency system 10 includes a filter 12 with an integratedtemperature sensor 14, an over temperature circuit 16, and a radiofrequency signal path 18.

The filter 12 can filter an RF signal. Transmit filters can receive RFsignals having a higher signal level than receive filters in typical RFsystems. Accordingly, it can be advantageous to provide over temperatureprotection for transmit filters. Thus, the filter 12 can be a transmitfilter, such as a transmit filter of a duplexer. The filter 12 can be aSAW filter, for example. In some instances, the filter 12 can be a BAWfilter, such as an FBAR filter. The filter 12 can include one or moreSAW resonators and one or more BAW resonators in some applications.

The integrated temperature sensor 14 can be on the same filter substrateas elements of the filter 12 that perform filtering. As an example,acoustic wave resonators of the filter 12 and the temperature sensor 14can be on the same filter substrate. The integrated temperature sensor14 can be any suitable temperature sensor. For instance, the temperaturesensor 14 can be an RTD. The resistive thermal device can include aplurality of metal strips arranged as a grating for one or more surfaceacoustic wave resonators. Such a resistive thermal device can beserpentine in plan view. In some other instances, the temperature sensor14 can include a thermocouple. The temperature sensor 14 can include oneor more resonators having a resonant frequency that changes withtemperature in certain instances. The temperature sensor 14 can includea temperature sensor in accordance with any of the principles andadvantages discussed herein as suitable.

Although the filter 12 is illustrated as providing a signal indicativeof temperature to the over temperature circuit 16 by way of a dedicatedsignal line in FIG. 1A, the signal indicative of temperature can beprovided to the over temperature circuit 16 in a variety of ways. Forinstance, the over temperature circuit 16 can obtain an indication oftemperature from the temperature sensor 14 from an input of the filter12, an output of the filter 12, or from a temperature sensor 14 arrangedbetween two ports of the filter 12. In some instances, a filteringcircuit, such as an RC circuit or an LC circuit, can be coupled betweenan input of the filter 12 arranged to provide an indication oftemperature and the over temperature circuit 16. According to some otherinstances in which the filter 12 includes two ports across which thetemperature sensor 14 is coupled, temperature sensors in differentfilters can be daisy chained. Such a daisy chain can reduce the numberof I/O signals to the over temperature circuit 16 in certain instances.The over temperature circuit 16 can obtain an indication of temperaturefrom a temperature sensor 14 of the filter 12 in accordance with any ofthe principles and advantages of the example acoustic wave filters ofFIGS. 5A to 11.

The over temperature circuit 16 can detect whether an output of thetemperature sensor 14 satisfies a threshold. This can include detectingwhether the temperature of the filter 12 is close to a temperature thatcan damage the filter. The over temperature circuit 16 can reduce aninput power at an input port of the filter 12 in response to detectingthat a temperature of the filter 12 is relatively close to a temperaturethat could damage the filter 12 or otherwise impair the function of thefilter 12. For instance, the over temperature circuit 16 can reduce asignal level of a radio frequency signal provided to the filter 12 inresponse to the output of the temperature sensor satisfying thethreshold. In certain applications, the over temperature circuit 16 cancause a duty cycle of a power amplifier in the RF signal path 18 to bereduced in response to detecting that a temperature associated with thefilter 12 satisfies a threshold. The over temperature circuit 16 canprovide an output signal to the RF signal path 18 that causes the radiofrequency signal provided to the filter 12 to be reduced. The overtemperature circuit 16 can reduce a power level of the radio frequencysignal provided to the filter 12 to a safe level. The safe level canrepresent a power level that is below a specified upper bound on a powerlevel of an input to the filter 12. A radio frequency signal at the safelevel should not damage the filter 12. The over temperature circuit 16can reduce the amplitude of the radio frequency signal provided to thefilter 12 to be approximately zero in some instances. This caneffectively cause the filter 12 to stop filtering the radio frequencysignal provided by the RF signal path 18.

The over temperature circuit 16 can be implemented by any suitablecircuitry arranged to detect that an indication of temperature from thetemperature sensor 14 satisfies a threshold and to assert an overtemperature signal in response. The over temperature circuit 16 can beimplemented by a controller, for example. The over temperature circuit16 can be implemented by resistors arranged in a bridge configurationwith a resistive thermal device temperature sensor, as another example.A variety of different circuits arranged to detect a change inresistance of a resistive thermal device temperature sensor can beimplemented.

The RF signal path 18 can be any suitable signal path arranged toprovide a radio frequency signal to the filter 12. The RF signal path 18can be a transmit path. The RF signal path 18 can include a poweramplifier, for example.

FIG. 1B is a schematic diagram of an example over temperature circuit 19according to an embodiment. As shown in FIG. 1B, the over temperaturecircuit 19 can include a comparator arranged to compare an indication oftemperature TEMP with a reference signal V_(REF). These signals can bevoltage signals. The reference signal V_(REF) can represent a thresholdat which the indication of temperature TEMP is at or near a temperaturecorresponding to an over temperature condition. When the indication oftemperature TEMP exceeds the reference signal V_(REF), an overtemperature signal OUT can be asserted to indicate an over temperaturecondition.

FIG. 2A is a schematic diagram of a radio frequency system 20 with overtemperature protection according to another embodiment. The radiofrequency system 20 is like the radio frequency system 10 of FIG. 1A,except that the radio frequency system 20 includes a power amplifier 22arranged to receive a bias signal from the over temperature circuit 16.The over temperature circuit 16 of FIG. 2A can provide the bias signalso as to attenuate the output of the power amplifier 22 in response todetecting that a temperature associated with the filter 12 satisfies athreshold. The bias signal can reduce the gain of the power amplifier 22to approximately zero in certain instances.

FIG. 2B is a schematic diagram of a radio frequency system 25 with overtemperature protection according to another embodiment. The radiofrequency system 25 is like the radio frequency system 20 of FIG. 2A,except that the over temperature circuit 16 provides an over temperaturesignal to a supply circuit 27 instead of the power amplifier 22. Thesupply circuit 27 can reduce and/or limit a supply voltage to the poweramplifier 22 in response to the over temperature signal being asserted.In some instances, the supply voltage circuit can bring a supply voltagefor the power amplifier 22 close to 0 Volts in response to the overtemperature circuit 16 detecting that a temperature associated with thefilter 12 satisfies a threshold. The supply circuit 27 can include anenvelope tracking modulator in certain applications. In such instances,the over temperature signal from the over temperature circuit 16 canlimit a supply voltage provided by the envelope tracking modulator.

FIG. 3 is a schematic diagram of a radio frequency system 30 with overtemperature protection according to another embodiment. The radiofrequency system 30 is like the radio frequency system 10 of FIG. 1A,except that the radio frequency system 30 includes a power amplifier 22and a variable gain amplifier 32 arranged to receive an input from theover temperature circuit 16. The over temperature circuit 16 of FIG. 3can adjust a gain of the variable gain amplifier 32 to cause the outputof the power amplifier 22 to be attenuated in response to detecting thata temperature associated with the filter 12 satisfies a threshold. Thevariable gain amplifier 32 can be included in a transmitter, such as atransmitter of a transceiver.

FIG. 4 is a schematic diagram of a radio frequency system 40 with overtemperature protection according to another embodiment. The radiofrequency system 40 is like the radio frequency system 20 of FIG. 2A,except that the radio frequency system 40 includes a switch 42 coupledbetween the power amplifier 22 and the filter 12 and an output of theover temperature circuit 16 is provided to the switch 42. The overtemperature circuit 16 of FIG. 4 can control the switch 42 so as toattenuate the output of the power amplifier 22 in response to detectingthat a temperature associated with the filter 12 satisfies a threshold.In some instances, the over temperature circuit 42 can turn off theswitch 42 in response to detecting that the temperature associated withthe filter 12 satisfies the threshold. This can decouple the output ofthe power amplifier 22 from an input of the filter 12. When the outputof the power amplifier 22 is decoupled from the input of the filter 12,this can reduce the amplitude of the radio frequency signal provided tothe input of the filter 12 to approximately zero. The illustrated switch42 can represent a throw of a multi-throw radio frequency switch.

Aspects of this disclosure can be implemented in an acoustic wavefilter. For instance, an acoustic wave filter can include a plurality ofresonators and a resistive thermal device. The resistive thermal devicehas a resistance that varies with temperature. Accordingly, theresistive thermal device can be a temperature sensor. Some or all of theresonators of an acoustic wave filter and the resistive thermal devicecan be implemented on a common filter substrate. The resonators caninclude SAW resonators and/or BAW resonators. In a surface acoustic wavefilter, any of the resistive thermal devices of FIGS. 5A to 9 can beconfigured as a reflective grating for one or more surface acoustic waveresonators of the surface acoustic wave filter. FIGS. 5A to 9 illustrateexample acoustic wave filters with resistive thermal devices. Anysuitable combination of features of these acoustic wave filters can beimplemented together. Any of the principles and advantages of theseacoustic wave filters can be implemented in any of the radio frequencysystems of FIGS. 1A, 2A, 2B, 3, and 4, for example.

FIG. 5A is a schematic diagram of an acoustic wave filter 50 with aresistive thermal device according to an embodiment. As illustrated, theacoustic wave filter 50 includes resonators 51, 52, 53, 54, and 55,resistive thermal device 56, and capacitor 57. In the acoustic wavefilter 50, the resistive thermal device 56 is connected to the transmitport Tx. This can enable temperature sensing without significantlyincreasing insertion loss and without adding an additional port of theacoustic wave filter 50.

The resonators 51, 52, 53, 54, and 55 are together arranged as a filterconfigured to filter an RF signal. As illustrated, the filter is aladder filter. Resonators 51, 53, and 55 are arranged as seriesresonators. Resonators 52 and 54 are arranged as shunt resonators. Theacoustic wave filter 50 can include any suitable number of seriesresonators and any suitable number of shunt resonators. The resonators51, 52, 53, 54, and 55 are illustrated as one port resonators. In someinstances, one or more resonators of the acoustic wave filter 50 can beother types of resonators.

In the acoustic wave filter 50, the resistive thermal device 56 iscoupled to a transmit port Tx. As illustrated, all of the illustratedresonators of the acoustic wave filter 50 are coupled between theresistive thermal device 56 and the antenna port ANT. The resistivethermal device 56 can have a resistance of at least 500Ω or at least 1kΩ, for example. In some instances, the resistance of the resistivethermal device 56 is in a range from 1 kΩ to 10 kΩ.

The resistive thermal device 56 of FIG. 5A is connected in shunt with adirect current (DC) blocked filter input to allow temperature monitoringwithout extra device connections. The transmit port Tx can receive aradio frequency signal in which a DC component is blocked. For instance,a DC blocking capacitor can be disposed in a signal path to the transmitport Tx of the acoustic wave filter 50.

As illustrated, the capacitor 57 is arranged in series between thetransmit port Tx and the resonators 51, 52, 53, 54, and 55. In theacoustic wave filter 50, the capacitor 57 is coupled between theresistive thermal device 56 and the resonators 51, 52, 53, 54, and 55.The capacitor 57 can block a DC voltage associated with the resistivethermal device 56 from the resonators 51, 52, 53, 54, and 55. Thecapacitor 57 can be manufactured in a precise and repeatable manner. Thecapacitor 57 can have a capacitance of a few picofarads (pF), forexample. In some instances (not illustrated), a shunt capacitor can alsobe included in parallel with the resistive thermal device 56 to providelow pass filtering. Such a low pass filter can reduce cross-bandisolation issues in some instances.

With the resistive thermal device 56 connected to the transmit port Txof the acoustic wave filter 50, an LC circuit and/or an RC circuit canbe coupled between the transmit port Tx and an over temperature circuit.This can provide filtering such that the over temperature circuit canreceive a DC component for sensing temperature. The filtering can blockan RF signal component from being provided to the over temperaturecircuit. The filtering circuit (e.g., the LC circuit or RC circuit becoupled between the transmit port Tx and an over temperature circuit)can be implemented external to the acoustic wave filter 50.

FIG. 5B is a schematic diagram of an acoustic wave filter 50 with aresistive thermal device 56 and off die circuit elements coupled to theresistive thermal device according to an embodiment. In FIG. 5B, an LCcircuit that includes an inductor 58 and a shunt capacitor 59 is coupledto the resistive thermal device 56. As illustrated, the LC circuit iscoupled to an input port of the acoustic wave filter 50. The LC circuitis implemented off of a die that includes the acoustic wave filter 50.The LC circuit can block the RF component of the signal at the transmitport Tx and pass the DC component of the signal at the transmit port Tx.Accordingly, an indication of temperature TEMP for an over temperaturecircuit can be a DC signal. The indication of temperature TEMP is ananalog signal in FIG. 5B.

FIG. 5C is a schematic diagram of an acoustic wave filter 60 with aresistive thermal device 56 and off die circuit elements coupled to theresistive thermal device according to an embodiment. The acoustic wavefilter 60 will be discussed in more detail in connection with FIG. 6. InFIG. 5C, the LC circuit that includes the inductor 58 and the shuntcapacitor 59 is coupled to an output port of the acoustic wave filter60. As illustrated, the output port is an antenna port ANT. The LCcircuit is implemented off of a die that includes the acoustic wavefilter 60. The LC circuit can block the RF component of the signal atthe antenna port ANT and pass the DC component of the signal at theantenna port ANT. Accordingly, an indication of temperature TEMP for anover temperature circuit can be a DC signal. The indication oftemperature TEMP is an analog signal in FIG. 5C.

FIG. 6 is a schematic diagram of an acoustic wave filter 60 with aresistive thermal device according to another embodiment. The acousticwave filter 60 is like the acoustic wave filter 50 of FIG. 5A, exceptthat the resistive thermal device 56 of the acoustic wave filter 60 isconnected to an output port of the filter. Accordingly, the resonators51, 52, 53, 54, and 55 of the acoustic wave filter 60 are coupledbetween the resistive thermal device 56 and the transmit port Tx. In theacoustic wave filter 60, the capacitor 57 is also connected in seriesbetween an output port of the filter 60 and the resonators 51, 52, 53,54, and 55. As shown in FIG. 6, the output port can be an antenna portANT. In the acoustic wave filter 60, the capacitor 57 is coupled betweenthe resistive thermal device 56 and the resonators 51, 52, 53, 54, and55. The capacitor 56 can block a DC voltage associated with theresistive thermal device 56 from the resonators 51, 52, 53, 54, and 55.The acoustic wave device 60 can enable temperature sensing withoutsignificantly increasing insertion loss and an existing filter port canbe used for temperature sensing.

FIG. 7 is a schematic diagram of an acoustic wave filter 70 with aresistive thermal device according to another embodiment. The acousticwave filter 70 is like the acoustic wave filter 50 of FIG. 5A and theacoustic wave filter 60 of FIG. 6, except that the capacitor 57 isomitted and the resistive thermal device 56 of the acoustic wave filter70 has a first end connected to a first dedicated sensing portT_(SENSE1) and a second end connected to a second dedicated sensing portT_(SENSE2). An over temperature circuit can detect a resistance of theresistive thermal device 56 of the acoustic wave filter 70 across thefirst dedicated port and the second dedicated port. The resistivethermal device 56 of the acoustic wave filter 70 can be daisy chainedwith one or more resistive thermal devices of other acoustic wavefilters. Implementing such a daisy chain can reduce inputs to an overtemperature circuit configured to detect an over temperature conditionassociated with a plurality of acoustic wave filters relative to theacoustic wave filter 60 of FIG. 6. Alternatively or additionally, such adaisy chain can reduce a number of over temperature circuits used todetect over temperature conditions associated with a plurality ofacoustic wave filters.

FIG. 8 is a schematic diagram of an acoustic wave filter 80 with aresistive thermal device 56 according to another embodiment. Theacoustic wave filter 80 is like the acoustic wave filter 70 of FIG. 7,except that the resistive thermal device 56 of the acoustic wave filter80 is connected between a dedicated temperature sensing port T_(SENSE)and ground. An over temperature circuit can be coupled to the dedicatedtemperature sensing port T_(SENSE) and detect a resistance of theresistive thermal device 56 of the acoustic wave filter 80.

FIG. 9 is schematic diagram of an acoustic wave filter 90 with resistivethermal devices according to an embodiment. The acoustic wave filter 90is like the acoustic wave filter 80 of FIG. 8, except that the acousticwave filter 90 includes a plurality of resistive thermal devices 56 ₁ to56 _(N) in parallel with each other. The resistive thermal devices 56 ₁to 56 _(N) are each connected between a dedicated temperature sensingport T_(SENSE) and ground. With a plurality of resistive thermal devices56 ₁ to 56 _(N) in parallel, a total resistance change versustemperature can decrease. Accordingly, finer changes in temperature canbe detected relative to a single resistive thermal device. An overtemperature circuit can be coupled to the dedicated temperature sensingport T_(SENSE) and detect a resistance of the resistive thermal devices56 ₁ to 56 _(N) of the acoustic wave filter 90.

While FIGS. 5A to 9 illustrate filters that include a resistive thermaldevice, other suitable temperature sensors can be included in anacoustic wave filter. Such other suitable temperature sensors can beused to implement any suitable principles and advantages of overtemperature protection discussed herein. An acoustic wave filter caninclude an integrated temperature that includes, for example, athermocouple, one or more resonators, a thermistor, or any combinationthereof. A thermistor can be implemented in place of a resistive thermaldevice in any of FIGS. 5A to 9. FIGS. 10 and 11 illustrate exampleacoustic wave filters with integrated temperature sensors. Any suitablecombination of the acoustic wave filters of FIGS. 5A to 11 can beimplemented together with each other. For instance, two different typesof temperature sensors can be included in an acoustic wave filter. Anyof the principles and advantages of the acoustic wave filters of FIGS.10 to 11 can be implemented in any of the radio frequency systems ofFIGS. 1A, 2A, 2B, 3, and 4.

FIG. 10 is schematic diagram of an acoustic wave filter 100 with anintegrated temperature sensor that includes a thermocouple 101 accordingto an embodiment. The acoustic wave filter 100 is like the acoustic wavefilter 80 of FIG. 8 except that the acoustic wave filter 100 includesthe thermocouple 101 in place of a resistive thermal device 56. An overtemperature circuit can be coupled to the thermocouple 101 to detect atemperature associated with the acoustic wave filter 100. Thethermocouple 101 can include two materials forming electrical junctionsat different temperature. The thermocouple 101 can provide atemperature-dependent voltage that is an indication of temperature. Thethermocouple 101 can include metals, such as aluminum and molybdenum,which can be metals in a SAW filter stack.

FIG. 11 is schematic diagram of an acoustic wave filter 110 with anintegrated temperature sensor that includes a resonator 112 according toan embodiment. The acoustic wave filter 110 is like the acoustic wavefilter 100 of FIG. 10 except that the acoustic wave filter 110 includesa resonator 112 instead of a thermocouple 101. The resonator 112 caninclude a SAW resonator or a BAW resonator, for example. The resonator112 can be a standalone device. A change in temperature of the acousticwave filter 110 can cause a resonant frequency of the resonator 112 tochange. An over temperature circuit can detect the change in resonantfrequency of the resonator 112. The resonator 112 can be interrogatedwith a different frequency that a frequency of an RF signal provided tothe transmit port Tx of the acoustic wave filter 110. The resonator 112can be arranged in shunt or in series. If arranged in series, theresonator can be coupled across two ports of the acoustic wave filter.

In some instances, temperature sensing ports of a plurality of acousticwave filters 110 can be daisy chained. To differentiate indications oftemperature associated with different daisy chained filters, thetemperature sensing resonator of each filter can be interrogated with adifferent frequency, for example. As another example, indications oftemperature associated with different daisy chained temperature sensorscan be differentiated by having respective temperature sensingresonators interrogated at different times.

Acoustic wave filters can be implemented in a multiplexer in an RFsystem. For instance, a duplexer including a transmit filter and areceive filter coupled to a common node can each include an acousticwave filter. Any suitable principles and advantages discussed herein canbe implemented in other multiplexers, such as quadplexers, hexaplexers,octoplexers, and the like. Transmit signals can have relatively highpower. When the power gets sufficiently high, such as in certain highVWSR scenarios, the transmit filter can be damaged. Accordingly,temperature sensing in accordance with any suitable principles andadvantages discussed herein can be implemented in association with atransmit filter included in a multiplexer. Alternatively, temperaturesensing in accordance with any suitable principles and advantagesdiscussed herein can be implemented in association with a stand-alonetransmit filter. For instance, such a stand-alone transmit filter can beimplemented in time-domain duplex (TDD) applications. As one example,temperature sensing in accordance with any suitable principles andadvantages discussed herein can be implemented in a stand-alone Band 41transmit filter in a TDD application.

FIG. 12A is schematic block diagram of a duplexer 120 that includes atransmit filter 122 with an integrated temperature sensor 14 accordingto an embodiment. The duplexer 120 also includes a receive filter 124that is coupled to the transmit filter 122 at an antenna node ANT. Thetransmit filter 122 can include an acoustic wave filter with anintegrated temperature sensor 14 in accordance with any principles andadvantages discussed herein.

Although certain embodiments discussed herein relate to transmit filterswith integrated sensors, any suitable principles and advantagesdiscussed herein can be applied to receive filters. A receive filter caninclude an integrated temperature sensor for a variety of reasons. Insome instances, an integrated sensor of a receive filter can be used tocompensate for a variation in a frequency response of the receive filterover temperature.

FIG. 12B is schematic block diagram of a duplexer 125 that includes atransmit filter 122 with a first integrated temperature sensor 14A and areceive filter 126 with a second integrated temperature sensor 14Baccording to an embodiment. The transmit filter 122 and the receivefilter 126 are both coupled to an antenna node ANT. The integratedtemperature sensor 14B of the receive filter 126 can be implemented inaccordance with any suitable principles and advantages discussed herein.FIG. 12B illustrates both a transmit filter and a receive filter of aduplexer can include integrated temperature sensors.

FIG. 12C is schematic block diagram of a duplexer 127 that includes areceive filter 126 with an integrated temperature sensor 14 according toan embodiment. The duplexer 127 also includes a transmit filter 128 thatis coupled to the receive filter 126 at an antenna node ANT. Theillustrated transmit filter 128 does not include an integratedtemperature sensor. FIG. 12C illustrates that in certain applications aduplexer can include a receive filter with an integrated temperaturesensor and a transmit filter without an integrated temperature sensor.

Some RF systems can include forward power detection circuitry to monitorthe output power of the RF system and/or a device that includes the RFsystem. An indication of the detected forward output power can be usedin a feedback loop of a power amplifier control system to maintain adesired forward output power level. As VSWR in an RF system increases(e.g., a mobile phone including the RF system is placed in a metal deskdrawer), the forward transmit power of the RF system typically decreasescorrespondingly. The power amplifier control system can cause the poweramplifier drive level to increase to compensate for such a decrease inforward transmit power. In a filter (e.g., a SAW filter) arranged tofilter an output of the power amplifier, this increase in RF input powerto the filter can lead to more dissipated power within the filter,manifesting as an increase in the temperature. For filters with anegative temperature coefficient of frequency (TCF), this should resultin a downward frequency shift of the pass band. If the RF system isoperating at a frequency where the filter frequency response has arelatively steep negative slope, such as at the upper corner of the passband, the downward shift of the pass band can cause a furthersignificant increase in insertion loss. This can cause additional powerdissipation within the filter and raise the temperature even more, aswell as reduce output power, thereby causing the feedback loop tofurther increase the input power to the filter. The net result can be apositive feedback loop that can result in thermal runaway, which canlead to irreparable damage to the filter. The over temperatureprotection discussed herein can prevent such damage by sensing atemperature associated with a filter and reducing a signal level of aninput to the filter in response to the temperature satisfying athreshold.

FIG. 13 is graph of a transfer function of a duplexer over frequency inwhich a shift in the transfer function can result in an out of bandblocker failure. The nominal response shown in FIG. 13 corresponds totypical operation. The shifted response corresponds to a high VSWRsituation in which temperature of the duplexer increases. As shown inFIG. 13, the frequency response of the transmit filter can be shifteddown in frequency as the temperature of the filter increases. This cancause an out of band blocker failure at high temperature. The overtemperature protection discussed herein can prevent such a failure bysensing a temperature associated with a filter and reducing a signallevel of an input to the filter in response to the temperaturesatisfying a threshold.

FIG. 14 is a graph that zooms in on transmit and receive pass bands ofthe graph of FIG. 13. As shown in FIG. 14, the upper edge of transmitpassband of the shifted response can be close to or at a sharp drop inthe transfer function. This can be undesirable. The over temperatureprotection discussed herein can reduce an amount by which the transferfunction shifts and/or prevent the illustrated shifted response fromoccurring.

FIG. 15 is a simulated heat map of a surface acoustic wave duplexer.This heat map shows that certain parts of a SAW duplexer are hotter thanother parts. A temperature sensor, such as an RTD, can be positionedrelatively close to a relatively hot area of the SAW duplexer.Accordingly, the temperature sensor can sense a temperature that is ator near a maximum temperature of the SAW duplexer.

FIG. 16A is a block diagram of a layout of an acoustic wave filter 160with an integrated resistive thermal device according to an embodiment.As shown in FIG. 16, the acoustic wave filter 160 includes a filtersubstrate 162 on which resonators 164, a resistive thermal device 165, aground contact 166, and a transmit port contact 167 are disposed. Theresistive thermal device 165 can be positioned near a relatively hightemperature portion of the acoustic wave filter 160. The resistivethermal device 165 can also be positioned close to the ground contact166 and the transmit port contact 167 in certain instances. Theresistive thermal device 165 can be connected between the transmit portcontact 167 and the ground contact 166. The resistive thermal device 165of the acoustic wave filter 160 can be connected like the resistivethermal device 56 of the acoustic wave filter 50 of FIGS. 5A and 5B. Thetransmit port contact 167 can include a pin, for example. The acousticwave filter 160 can be embodied on a single die.

FIG. 16B is a block diagram of a layout of an acoustic wave filter 168with an integrated resistive thermal device according to anotherembodiment. The acoustic wave 168 is like the acoustic wave filter 160of FIG. 16A except that the acoustic wave filter includes a dedicatedtemperature sensing contact 169. The resistive thermal device 165 can beconnected between the dedicated temperature contact port 169 and theground contact 166. The resistive thermal device 165 of the acousticwave filter 168 can be connected like the resistive thermal device 56 ofthe acoustic wave filter 80 of FIG. 8. In the acoustic wave filter 168,the resistive thermal device 165 can be configured as a reflectivegrating for one or more acoustic wave resonators of the resonators 164.

FIG. 17A illustrates a serpentine resistive thermal device configured asa grating for a surface acoustic wave resonator 170 according to anembodiment. FIG. 17A illustrates a 1-port SAW resonator. The surfaceacoustic wave resonator 170 includes a first grating 172, a secondgrating 174, and an interdigital transducer 176. The first grating 172,the second grating 174, and the interdigital transducer 176 can bedisposed on a piezoelectric substrate. The piezoelectric substrate canbe a lithium niobate substrate or a lithium tantalate substrate, forexample. The first grating 172 and the second grating 174 are disposedon opposing sides of the interdigital transducer 174.

The first grating 172 is arranged as a resistive thermal device thatincludes metal strips arranged in series with each other. Theillustrated resistive thermal device is serpentine in plan view. Theresistive thermal device can include any suitable number of metal stripsin series with each other to provide a desired resistance. The resistivethermal device can be coupled between a transmit port Tx and ground asillustrated. Alternatively, the thermal resistive device can be arrangedbetween different nodes (for example, as shown in FIGS. 6 to 9). Themetal strips of the resistive thermal device can include aluminum. Themetal strips of the resistive thermal device can include the samematerial as metal strips of the interdigital transducer 176 and/or thesecond grating 174.

FIG. 17B illustrates a serpentine resistive thermal device configured asa grating for a surface acoustic wave resonator 178 according to anotherembodiment. The surface acoustic wave resonator 178 is like the surfaceacoustic wave resonator of FIG. 17A, except that the resistive thermaldevice is connected between a dedicated temperature sensing portT_(SENSE) and ground.

FIG. 18 illustrates a portion 180 of a surface acoustic wave filter withan integrated resistive thermal device according to an embodiment. Thesurface acoustic wave filter includes a substrate 182, a resistivethermal device 183 on the substrate 182, interdigital transducers 184and 186 on the substrate 182, a transmit port 187, and a ground pad 188Aand 188B. As illustrated, the resistive thermal device 183 can functionas grating for two resonators. The restive thermal device 183 isconfigured as an acoustic reflector for the first interdigitaltransducer 184 and the second interdigital transducer 186. Theinterdigital transducers 184 and 186 can be included in differentresonators of a ladder filter. While the resistive thermal device 183can function as a grating for two resonators as shown in FIG. 18, aresistive thermal device can function as a grating for any suitablenumber of SAW resonators. In some instances, gratings from several SAWresonators can be coupled together to form an resistive thermal devicehaving a higher resistance and an averaged thermal response relative toan resistive thermal device formed of a grating for a single resonator.

In FIG. 18, the resistive thermal device 183 includes metal stripsarranged in series between the transmit port 187 and ground. The metalstrips of the resistive thermal device 183 can be formed of the samematerial as metals strips of the interdigital transducer 184. Such metalstrips can be formed of any suitable metallic material. For instance,the metal strips can include aluminum (e.g., the metal strips can bealuminum or an alloy that includes aluminum). Portions of the ground pad188A and 188B that can be electrically connected together areillustrated in FIG. 18.

FIG. 19 illustrates a larger portion 190 of the surface acoustic wavefilter of FIG. 18. In FIG. 19, some portions of the surface acousticwave filter are illustrated as blocks. As shown in FIG. 19, the surfaceacoustic wave filter includes resonator portions 194, 196, 197, and 198.One or more of the resonator portions can include resonators in parallelwith each other configured to function as a composite resonator.Alternatively or additionally, one or more of the resonator portions caninclude two or more separate resonators of a ladder filter. FIG. 19 alsoillustrates ground pad 188 that includes ground pad portions 188A and188B shown in FIG. 18. In addition, more of transmit port 187 isillustrated in FIG. 19 than in FIG. 18.

Acoustic wave filters that include a temperature sensor can beimplemented in a variety of modules. Any of the principles andadvantages of an acoustic wave filter that includes a temperature sensorand/or an over temperature circuit can be implemented in a module assuitable. Modules can include circuits included within a common package.Accordingly, such modules can be referred to as packaged modules. Amodule can include one or more acoustic wave filters with an integratedtemperature sensor, an over temperature circuit, one or more multi-throwradio frequency switches, one or more power amplifiers, or any suitablecombination thereof. Such modules can be referred to as radio frequencymodules, as these modules are configured to process a radio frequencysignal. FIGS. 20 to 23 illustrate example modules with over temperatureprotection. Any suitable combination of features of these modules can beimplemented. FIGS. 20 to 22 are examples of front end modules withintegrated filters and radio frequency switches. FIG. 23 is an exampleof a module that includes a power amplifier with integrated duplexersand radio frequency switches.

FIG. 20 is a schematic block diagram of a module 200 that includesfilters 202 _(A) to 202 _(N) and an over temperature circuit 16according to an embodiment. The filters 202 _(A) to 202 _(N) can betransmit filters. Some or all of the filters 202 _(A) to 202 _(N) can beincluded in duplexers or other suitable multiplexers. A multi-throwradio frequency switch 204 can provide a radio frequency signal to atransmit port of a filter of the filters 202 _(A) to 202 _(N). Themulti-throw radio frequency switch 204 can be a band select switch, forexample. The filters 202 _(A) to 202 _(N) can be SAW filters, forexample. Any suitable number of filters 202 _(A) to 202 _(N) can beincluded for a particular application. Some or all of the filters 202_(A) to 202 _(N) can include a temperature sensor coupled to the overtemperature circuit 16. The filters 202 _(A) to 202 _(N) can be bandpass filters with different pass bands and/or filter characteristics(e.g., out of band attenuation, in band attenuation, symmetry orasymmetry about the pass band, etc., or any combination thereof).

The over temperature circuit 16 can detect that the temperature of afilter of the filters 202 _(A) to 202 _(N) satisfies a threshold.Responsive to detecting that the temperature of the filter satisfies thethreshold, the over temperature circuit 16 can cause the multi-throwradio frequency switch 204 to decouple a radio frequency signal receivedat a common node from the filter in certain instances. Alternatively,the over temperature circuit 16 can assert an over temperature signalprovided to circuitry arranged to generate the radio frequency signalprovided to the common node of the multi-throw radio frequency switch204 responsive to detecting that the temperature of the filter satisfiesthe threshold. Asserting such an over temperature signal can reduce thepower level and/or signal level of the radio frequency signal.

FIG. 21 is a schematic block diagram of a module 210 that includesfilters and an over temperature circuit according to another embodiment.The module 210 is like the module 200 of FIG. 20 except that the module210 includes a multi-throw radio frequency switch 214 instead of themulti-throw radio frequency switch 204 of FIG. 20. The multi-throw radiofrequency switch 214 has throws coupled to respective outputs of thefilters 202 _(A) to 202 _(N). The multi-throw radio frequency switch 214can provide an output of a selected filter of the filters 202 _(A) to202 _(N) to a common node, such as an antenna port of the module 210.Responsive to detecting that the temperature of a filter satisfies thethreshold, the over temperature circuit 16 assert an over temperaturesignal provided to circuitry arranged to generate the radio frequencysignal provided to an input port of the filter. Asserting such an overtemperature signal can reduce the power level and/or signal level of aradio frequency signal provided to the input port.

FIG. 22 is a schematic block diagram of a module 220 that includesfilters and an over temperature circuit according to another embodiment.The module 220 includes a first multi-throw switch 204 and a secondmulti-throw switch 214. FIG. 22 illustrates that features of FIGS. 20and 21 can be included within the same module.

FIG. 23 is a schematic block diagram of a module 230 that includes afilter and an over temperature circuit according to another embodiment.As illustrated, the module 230 includes power amplifiers 232A and 232B,select switches 234A and 234B, duplexers 236A, 236B, 236C, and 236D, anantenna switch 238, and an over temperature circuit 16.

The power amplifier 232A is arranged to amplify a first radio frequencysignal RF_IN1. Similarly, the power amplifier 232B is arranged toamplify a second radio frequency signal RF_IN2. These power amplifierscan amplify radio frequency signals having different characteristics.The different characteristics can include more or more of being withindifferent frequency bands, being at different power levels, beingassociated with different linearity and/or power added efficiency, orbeing associated with different modes of operation. In the module 230,one of the power amplifiers 232A and 232B can amplify a radio frequencysignal at a given time. In some instances, two power amplifiers in amodule can amplify different radio frequency signals concurrently. Forinstance, in a carrier aggregation mode, the two power amplifiers canconcurrently amplify radio frequency signals that are within differentfrequency bands and that are combined using a frequency multiplexingcircuit, such as a diplexer.

The select switch 234A can selectively electrically couple an output ofthe power amplifier 232A to a transmit port of a selected duplexer 236Aor 236B. Similarly, the select switch 234B can selectively electricallycouple an output of the power amplifier 232B to a transmit port of aselected duplexer 236C or 236D. The antenna switch 238 can electricallycouple a selected duplexer to the antenna port ANT. In certainembodiments, the antenna switch can electrically couple two duplexers tothe antenna port ANT in a carrier aggregation mode.

One or more of the duplexers 236A to 236D can include a transmit filterwith an integrated temperature sensor. Such transmit filters can includeSAW resonators. While four duplexers are illustrated, any suitablenumber of duplexers can be implemented. For instance, 3 or moreduplexers can be coupled in a signal path between the select switch 234Aand the antenna switch 238A. Moreover, while duplexers are illustrated,any suitable multiplexer that includes a filter with an integratedtemperature sensor can be implemented. Such multiplexers can include atriplexer, a quadplexer, etc. in certain applications.

The over temperature circuit 16 can detect that the temperature of afilter of the duplexers 236A to 236N satisfies a threshold. Responsiveto detecting that the temperature of the filter satisfies the threshold,the over temperature circuit 16 can cause the select switch 234A and/or236B to decouple an amplified radio frequency signal received from apower amplifier from the filter. Alternatively, the over temperaturecircuit 16 can assert an over temperature signal provided to a poweramplifier and/or circuitry arranged to generate a radio frequency signalprovided to the power amplifier responsive to detecting that thetemperature of the filter satisfies the threshold. Asserting such anover temperature signal can reduce the power level and/or signal levelof the amplified radio frequency signal provided to the select switch.

FIG. 24 is a schematic block diagram of a wireless communication device240 that includes a radio frequency front end that can include a filterwith an integrated temperature sensor according to one or moreembodiments. The wireless communication device 240 can be any suitablewireless communication device. For instance, a wireless communicationdevice 240 can be a mobile phone, such as a smart phone. As illustrated,the wireless communication device 240 includes an antenna 242, an RFfront end 244, a transceiver 246, a processor 248, and a memory 249. Theantenna 242 can transmit RF signals provided by the RF front end 244.The antenna 242 can transmit carrier aggregated signals provided by theRF front end 244. The antenna 242 can provide received RF signals to theRF front end 244 for processing.

The RF front end 244 can include one or more power amplifiers, one ormore low noise amplifiers, RF switches, receive filters, transmitfilters, duplex filters, or any combination thereof. The RF front end244 can transmit and receive RF signals associated with any suitablecommunication standards. One or more filters with an integratedtemperature sensor in accordance with any suitable principles andadvantages discussed herein can be included in the RF front end 244. TheRF front end 244 can include an over temperature circuit in accordancewith any suitable principles and advantages discussed herein.

The RF transceiver 246 can provide RF signals to the RF front end 244for amplification and/or other processing. The RF transceiver 246 canalso process an RF signal provided by a low noise amplifier of the RFfront end 244. The RF transceiver 246 can include one or more circuitsconfigured to receive an over temperature signal and to reduce a powerlevel and/or signal level of a radio frequency signal provided to the RFfront end 244 in response to the over temperature signal being asserted.For instance, the RF transceiver 246 can provide one or more signals toa transmit path to adjust power of a carrier based on the overtemperature protection signal.

The illustrated RF transceiver 246 is in communication with theprocessor 248. The processor 248 can be a baseband processor. Theprocessor 248 can provide any suitable base band processing functionsfor the wireless communication device 240. The memory 249 can beaccessed by the processor 248. The memory 249 can store any suitabledata for the wireless communication device 240.

Any of the principles and advantages discussed herein can be applied toother systems, modules, filters, multiplexers, wireless communicationdevices, and methods not just to the systems, modules, filters,multiplexers, wireless communication devices, and methods describedabove. The elements and operations of the various embodiments describedabove can be combined to provide further embodiments. Some of theembodiments described above have provided examples in connection withsurface acoustic wave filters and/or transmit filters. However, theprinciples and advantages of the embodiments can be used in connectionwith any other systems, apparatus, or methods that benefit could fromany of the teachings herein. For instance, any of the principles andadvantages discussed herein can be implemented in connection withproviding over temperature protection for any suitable filter. Asanother example, any suitable principles and advantages of the acousticwave devices discussed herein can be implemented in radio frequencysystems to perform functions other than over temperature protection,such as compensating for a change in frequency response of a filter dueto changes in temperature. As one more example, any suitable principlesand advantages discussed herein can be applied to an integrated passivedevice die that includes a filter with an integrated temperature sensor.Any of the principles and advantages discussed herein can be implementedin association with RF circuits configured to process signals in a rangefrom about 30 kHz to 300 GHz, such as in a range from about 450 MHz to 6GHz.

Aspects of this disclosure can be implemented in various electronicdevices. Examples of the electronic devices can include, but are notlimited to, consumer electronic products, parts of the consumerelectronic products such as semiconductor die and/or packaged radiofrequency modules, electronic test equipment, uplink wirelesscommunication devices, personal area network communication devices, etc.Examples of the consumer electronic products can include, but are notlimited to, a mobile phone such as a smart phone, a wearable computingdevice such as a smart watch or an ear piece, a telephone, a television,a computer monitor, a computer, a router, a modem, a hand-held computer,a laptop computer, a tablet computer, a personal digital assistant(PDA), a vehicular electronics system such as an automotive electronicssystem, a microwave, a refrigerator, a vehicular electronics system suchas an automotive electronics system, a stereo system, a DVD player, a CDplayer, a digital music player such as an MP3 player, a radio, acamcorder, a camera such as a digital camera, a portable memory chip, awasher, a dryer, a washer/dryer, peripheral device, a clock, etc.Further, the electronic devices can include unfinished products.

Unless the context requires otherwise, throughout the description andthe claims, the words “comprise,” “comprising,” “include,” “including,”and the like are to generally be construed in an inclusive sense, asopposed to an exclusive or exhaustive sense; that is to say, in thesense of “including, but not limited to.” The word “coupled,” asgenerally used herein, refers to two or more elements that may be eitherdirectly coupled to each other, or coupled by way of one or moreintermediate elements. Likewise, the word “connected,” as generally usedherein, refers to two or more elements that may be either directlyconnected, or connected by way of one or more intermediate elements.Additionally, the words “herein,” “above,” “below,” and words of similarimport, when used in this application, shall refer to this applicationas a whole and not to any particular portions of this application. Wherethe context permits, words in the above Detailed Description of CertainEmbodiments using the singular or plural may also include the plural orsingular, respectively. The word “or” in reference to a list of two ormore items, is generally intended to encompass all of the followinginterpretations of the word: any of the items in the list, all of theitems in the list, and any combination of the items in the list.

Moreover, conditional language used herein, such as, among others,“can,” “could,” “might,” “may,” “e.g.,” “for example,” “such as” and thelike, unless specifically stated otherwise or otherwise understoodwithin the context as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or states. Thus, such conditional language is notgenerally intended to imply that features, elements and/or states are inany way required for one or more embodiments or that one or moreembodiments necessarily include logic for deciding whether thesefeatures, elements and/or states are included or are to be performed inany particular embodiment.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the disclosure. Indeed, the novel methods, apparatus, andsystems described herein may be embodied in a variety of other forms.Furthermore, various omissions, substitutions and changes in the form ofthe methods, apparatus, and systems described herein may be made withoutdeparting from the spirit of the disclosure. For example, circuit blocksdescribed herein may be deleted, moved, added, subdivided, combined,and/or modified. Each of these circuit blocks may be implemented in avariety of different ways. The accompanying claims and their equivalentsare intended to cover any such forms or modifications as would fallwithin the scope and spirit of the disclosure.

What is claimed is:
 1. A radio frequency system with over temperatureprotection, the radio frequency system comprising: a surface acousticwave filter configured to filter a radio frequency signal, the surfaceacoustic wave filter including an integrated temperature sensor, theintegrated temperature sensor including a resistive thermal devicehaving a resistance in a range from 1 kΩ to 10 kΩ, and the resistance isconfigured to change with temperature; a radio frequency signal pathconfigured to provide the radio frequency signal to the surface acousticwave filter; and an over temperature circuit configured to reduce apower level of the radio frequency signal responsive to an indication oftemperature provided by the temperature sensor satisfying a threshold.2. The radio frequency system of claim 1 wherein the resistive thermaldevice is arranged as a grating for at least one surface acoustic waveresonator of the surface acoustic wave filter.
 3. The radio frequencysystem of claim 1 wherein the resistive thermal device includes metalstrips arranged in series with each other.
 4. The radio frequency systemof claim 1 wherein the radio frequency signal path includes a poweramplifier operatively coupled to the surface acoustic wave filter, andthe over temperature circuit is configured to reduce the power level ofthe radio frequency signal by reducing a power level of an input signalto the power amplifier.
 5. The radio frequency system of claim 1 whereinthe radio frequency signal path includes a power amplifier operativelycoupled to the surface acoustic wave filter, and the over temperaturecircuit is configured to reduce the power level of the radio frequencysignal by attenuating an output signal of the power amplifier.
 6. Aradio frequency system with over temperature protection, the radiofrequency system comprising: a surface acoustic wave filter configuredto filter a radio frequency signal, the surface acoustic wave filterincluding an integrated temperature sensor; a radio frequency signalpath configured to provide the radio frequency signal to the surfaceacoustic wave filter, the radio frequency signal path including a poweramplifier operatively coupled to the surface acoustic wave filter; andan over temperature circuit configured to reduce a power level of theradio frequency signal responsive to an indication of temperatureprovided by the temperature sensor satisfying a threshold, and the overtemperature circuit being configured to reduce the power level of theradio frequency signal by decoupling an output of the power amplifierfrom an input to the surface acoustic wave filter using a switch.
 7. Theradio frequency system of claim 6 wherein the integrated temperaturesensor includes a resistive thermal device having a resistance thatchanges with temperature.
 8. The radio frequency system of claim 7wherein the resistance is in a range from 1 kΩ to 10 kΩ.
 9. The radiofrequency system of claim 6 wherein the resistive thermal is connectedbetween ground and an input port of the filter configured to receive theradio frequency signal.
 10. The radio frequency system of claim 6wherein the resistive thermal is connected between ground and an antennaport of the filter.
 11. A surface acoustic wave filter comprising:surface acoustic wave resonators configured to filter a radio frequencysignal; and a resistive thermal device having a resistance that changeswith temperature, the resistance being at least 500Ω, and the resistivethermal device including metal strips arranged in series with each otherand configured as a reflective grating of a surface acoustic waveresonator of the surface acoustic wave resonators.
 12. The surfaceacoustic wave filter of claim 11 wherein the resistive thermal device isconnected to a dedicated temperature sensing port of the surfaceacoustic wave filter.
 13. The surface acoustic wave filter of claim 11wherein the resistance is in a range from 1 kΩ to 10 kΩ.
 14. The surfaceacoustic wave filter of claim 11 wherein the resistive thermal device ispositioned adjacent to an area of the surface acoustic wave filterhaving a high power dissipation relative to other areas of the surfaceacoustic wave filter.
 15. The surface acoustic wave filter of claim 11wherein the resistive thermal device is configured as a reflectivegrating for a second surface acoustic wave resonator of the surfaceacoustic wave resonators.
 16. A packaged module comprising: a surfaceacoustic wave filter configured to filter a radio frequency signal, thesurface acoustic wave filter including an integrated temperature sensor,the integrated temperature sensor including a resistive thermal devicethat includes metal strips arranged in series with each other andconfigured as a reflective grating for at least one surface acousticwave resonator of the surface acoustic wave filter, and the resistivethermal device having a resistance of at least 500Ω; an over temperaturecircuit operatively coupled to the integrated temperature sensor, theover temperature circuit configured to reduce a power level of the radiofrequency signal responsive to an indication of temperature provided bythe temperature sensor satisfying a threshold; and a package enclosingthe surface acoustic wave filter and the over temperature circuit. 17.The packaged module of claim 16 wherein the over temperature circuit isconfigured to reduce the power level of the radio frequency signal bydecoupling an output of the power amplifier from an input to the surfaceacoustic wave filter using a switch.
 18. The packaged module of claim 16wherein the resistance is in a range from 1 kΩ to 10 kΩ.
 19. Thepackaged module of claim 16 wherein the surface acoustic wave filter isa transmit filter of a duplexer.
 20. The packaged module of claim 16further comprising a second acoustic wave filter and a multi-throwswitch enclosed within the package, the multi-throw switch having afirst throw coupled to the surface acoustic wave filter and a secondthrow coupled to the second acoustic wave filter.
 21. A surface acousticwave filter comprising: surface acoustic wave resonators configured tofilter a radio frequency signal; and a resistive thermal device having aresistance that changes with temperature, the resistive thermal devicebeing connected between an input port of the surface acoustic wavefilter and ground, and the resistive thermal device including metalstrips arranged in series with each other and configured as a reflectivegrating of a surface acoustic wave resonator of the surface acousticwave resonators.
 22. The surface acoustic wave filter of claim 21wherein the resistive thermal device has a resistance of at least 500Ω.23. The surface acoustic wave filter of claim 21 wherein the resistanceof the resistive thermal device is in a range from 1 kΩ to 10 kΩ. 24.The surface acoustic wave filter of claim 21 wherein the resistivethermal device is configured as a reflective grating for a secondsurface acoustic wave resonator of the surface acoustic wave resonators.